Order does matter: the combined effects of classical conditioning and verbal suggestions on placebo hypoalgesia and nocebo hyperalgesia.

ABSTRACT: In most experimental studies in which verbal suggestion and classical conditioning are implemented together to induce placebo effects, the former precedes the latter. In naturally occurring situations, however, the information concerning pain does not always precede but often follows the pain experience. Moreover, this information is not always congruent with experience. This study investigates whether the chronology of verbal suggestion and conditioning, as well as their congruence, affects placebo hypoalgesia and nocebo hyperalgesia. The effects induced in 15 groups were compared. The participants in 8 experimental groups were presented with verbal suggestions that were either congruent or incongruent with classical conditioning. The verbal suggestions were provided either before or after conditioning. In 2 other experimental groups, placebo conditioning or nocebo conditioning was implemented without any verbal suggestion; in 2 groups, verbal suggestion of hypoalgesia or hyperalgesia without conditioning was applied. The control groups without any suggestions or conditioning were also included. Placebo hypoalgesia induced by congruent procedures was significantly stronger when the suggestion of hypoalgesia preceded rather than followed conditioning. The order of the congruent procedures did not affect the magnitude of nocebo hyperalgesia. In the groups in which incongruent procedures were implemented, placebo hypoalgesia or nocebo hyperalgesia was in line with the direction of the last-used procedure, regardless of whether it was conditioning or verbal suggestion. The results show that not the type of the procedure (verbal suggestion or conditioning), but the direction of the last-used procedure shapes pain-related expectancies and determines placebo effects.

To Experience or to Be Informed? Classical Conditioning Induces Nocebo Hyperalgesia even when Placebo Analgesia Is Verbally Suggested-Results of a Preliminary Study.

OBJECTIVE: To investigate whether direct experience (i.e., classical conditioning) or verbal suggestion is more important in inducing nocebo hyperalgesia, five groups (total sample size, N = 99) were studied: conditioning, congruent conditioning, incongruent conditioning, verbal suggestion, and control. METHODS: Participants in groups with conditioning experienced more intensive pain stimuli after presentation of a white circle. In the congruent conditioning group, suggestion that the circle would precede more intensive pain stimuli was additionally provided, whereas in the incongruent conditioning group, the opposite suggestion was used. Control and verbal suggestion groups received pain stimuli of one intensity; however, the latter received suggestion that a circle would precede pain stimuli of higher intensity. RESULTS: The nocebo effect was observed in all conditioning groups, regardless of the verbal suggestions used. Moreover, the experience of hyperalgesia was able to nullify the effect of the verbal suggestion of analgesia. Incongruence between verbal suggestion and pain experience produced expectancies that affected nocebo hyperalgesia. CONCLUSIONS: The results of this preliminary study suggest that direct experience seems to be more important than verbal suggestion in inducing nocebo hyperalgesia.